UNCJD

So my Craigslist LS400 is in better shape now than when I got it. Using resources from these forums, I replaced the power steering pump, alternator, timing belt--WP--pulleys, EGR valve, plugs and wires, and resistance-tested one of the coils using a multimeter. Since the car sounds pretty good now, I got lazy and left the other coil alone. It's kind of buried.

When I got it, the dash lights and nothing electric worked. Could only start it using a battery charger. I found a blown alternator fuse, so I replaced that, and...wow, look at that, everything works. Battery was dead, so I left the charger on there and started it.

Once again, nothing electric works.

It blew the 120 amp alternator fuse there next to the ABS fuse. I know squat about automotive electrics, but I figure there's got to be a short or a ground failure somewhere between the alternator and that fuse. None of the other fuses or links are blown, just that one. Problem is...how do I find it?

The old PS pump bled all over everything under the care of the prior owner--it was carnage under there. The old alternator was black with PS fluid and every piece of dirt/dust that came within ten miles of it. I thought that might have had something to do with the original relay blowing. Now that the new alternator is on there and it's still doing it, I'm confused.

I picked up a couple 120A fusible links. My plan is to nuke the pigtail connector--which is still a little dirty--with degreaser, clean it the best I can, let it dry out and plug it back in. Replace the relay, start it, see if it blows again. I've ordered a new pigtail connector that should be here Saturday, but there's nothing visibly wrong, no exposed wires or anything, between the plug and the point where the wires disappear. Anybody else ever run into this? I want to check everything I can before I have to splice that new pigtail on.

I'm open to suggestions. The LS looks good in my garage and all, but I'd like to get it running before my wife makes me go live in it.

UNCJD

It's a 1995 with OBDII, US market, 251,600 miles. If that helps the diagnosis.

Yamae

Are you meaning the big 120 amp alternator fuse?
There isn't any relay named a 120 amp alternator relay.

The fuse opens when the battery connection is reversed, the cable is grounded or a dead alternator caused by the shorted rectifying diodes. Check the alternator measuring the resistance between the terminal B and the chassis.

UNCJD

Yes, the 120A fuse.

Funny about the reverse battery connection; when I first tried to juice it up, I actually had the charger cables reversed. The car honked at me. Maybe I blew it myself. I'll check in the morning.
Now that I think of it, I did the same thing when I checked the car out before buying it. I hope I blew the fuse myself. That would solve a lot.

Yamae

I hope there's no more damage. Reversing often causes multiple problems and you need to check others too.

UNCJD

What would you suggest? This poor car already suffered a lot before it met me.

Yamae

It depends on how much and how long the reverse current went through.
I suggest you to search the Net. There are many other people like you who accidentally reversed.
Search the Net and you will be finding problems caused by that by them. The worst scenario is the dead ECU but as long as the protection diode is not dead, it seldom happens.

UNCJD

Thanks for all your help. I'm going out there right now; I'll post the results.

UNCJD

Wow...glad I ran into you. Started up, didnt blow. Totally me reversing cables.
The Nak doesn't work now, but idk if it ever did.

dicer

It would be nice if the Title of this thread said Fuse and not Relay. Its just going to con Fuse everyone doing a search.

I do have a question why during the posts you made you at one point talk about fusible links or fuses that you got and then keep on with the relay gig ?

UNCJD

Because I thought they could be used interchangeably (the terms)-- I have since learned that they cannot.

UNCJD

I tried to edit the post to remove the wrong terminology, but it doesnt seem to have gone through.

UNCJD

Looked up "relay." Wow, not even close. Don't ask me where I got that.